Without seeing you and assessing you in person or over SKYPE, the problem is you are not moving your soft palate. It really is not that complicated. Tell your tongue to touch the roof of your mouth. As soon the area closest to the upper teeth has no ridges, that is the beginning of your soft palate. The rest of it in the back has a wiggly "U" hanging down which really lifts to create vocal variety. Try this exercise and do it 5 times with your eyes open and 5 times with your eyes closed. You are memorizing how it feels on the roof of your mouth. Say "hun-guh, hun-gee" pause and do it again. The back area of the soft palate will move for a "G" and a "K" swiftly. Whereever the "n" sound is of those two words, say your first and last name on the feeling. Also visualize your sounds are sitting on either side of a see-saw and move it up and down with the saying of your complete name.
A singer can overly belt so often and hold the high note so often with a straight, choir-boy light tone that excessive nasality in the voice begins. Using the voice for belting is just fine as long as voice exercises use flexibility and the full extremes of the singer's range BEFORE singing for that day. By using more "tummy" and "side ribs" support and singing on the beginning of the word's vowel formation, the excessive nasality leaves. I had a teenage client who was auditioning for a lead in a high school musical. The nasality in the song was gone by the 4th lesson. The client became the lead in 2016!